The present invention relates to valve metal oxides and more particularly relates to modified oxygen reduced valve metal oxides and methods to prepare the same.
Powders, such as those used as capacitor powders, can typically have poor agglomeration properties which creates problems when the powder needs to be pressed into an anode, for instance. Other times, powders can have poor flow properties or can have high surface hardness such that the pressing equipment used to press the powders is significantly worn by the surface of the powders. Thus, additives are used with the powders in order to modify the particle surface and thus improve the agglomeration of the particles, increase the flowability of the powders, minimize the wear on the processing equipment, enhance or not degrade post-pressing compact strength, and/or permit the easy removal of the compacted powder. With tantalum metal powders, certain additives may be used to primarily minimize wear since the industry has developed ways to produce agglomerated powders that have acceptable flow and crush strength. With valve metal oxides, such as oxygen reduced niobium oxides, (e.g. NbO), this material is a ceramic-type material with a high surface hardness compared to metals. The ceramic chemistry does not typically allow the rapid sintering to produce agglomerates used in metal processing and the diffusion behavior of ceramics is quite different than metals. Thus, the oxygen reduced valve metal oxides such as oxygen reduced niobium oxides need to be modified in order to provide the proper properties needed to form more commercially acceptable capacitor anodes.